When pregnant women take Tylenol, their children are more likely to be born with autism.

As many as 65 percent of women are said to take it during pregnancy. But Tylenol, the active ingredient of which is acetaminophen, has been linked in a new study out of Norway to causing autism in children. Expectant mothers who took the drug while pregnant to deal with headaches or mild fevers were found to be significantly more likely to bear children with behavioral problems, poor language and motor skills, and communication difficulties, compared to mothers who did not take the drug.

The study included data on 48,000 Norwegian children whose mothers participated in a survey evaluating their medication use at weeks 17 and 30 of pregnancy, as well as at six months after giving birth. The survey also included a follow-up that looked at the children’s developmental progress at three years of age, which was then compared to the mothers’ drug intake during the later stages of their pregnancies.

What was discovered was that some 4 percent of women took Tylenol for at least 28 days total during their pregnancies. And children born to this subset of mothers tended to have more functional and behavioral problems than children born to mothers who took less or no Tylenol. These same Tylenol-exposed children also tended to begin walking later than non-exposed children and had poorer communication and language skills.

“Our findings suggest that (acetaminophen) might not be as harmless as we think,” stated Ragnhild Eek Brandlistuen, lead author of the study from the University of Oslo in Norway. “Long-term use of (acetaminophen) increased the risk of behavior problems by 70 percent at age three. That is considerable.”

Johnson & Johnson, which owns the Tylenol brand, insists that the drug has an extensive track record of safety and has not been linked to premature birth and miscarriage. But the study, which was published in the International Journal of Epidemiology, suggests otherwise in terms of actual childhood development. It even compared Tylenol to other common pain medications, like ibuprofen, which were not found to induce behavioral problems.

“We always recommend that consumers carefully read and follow label instructions when using any over the counter medication,” admitted J&J in a statement. “In addition, our label notes if pregnant or breast-feeding, ask a health professional before use. Consumers who have medical concerns or questions about acetaminophen should contact their health care professional.”

Commenting on the study, Ann Z. Bauer, a doctoral candidate at the University of Massachusetts Lowell School of Health and Environment, inferred that pregnant women may want to avoid taking Tylenol and instead switch to an alternative. Her own research also suggests that acetaminophen may trigger these and various other symptoms in children, which categorically speaking can be defined as autism.

“The developmental problems seen in this study align with symptoms of autism spectrum disorder, though the children had not been diagnosed at age three,” writes Kathryn Doyle for Reuters Health.

Other research has also found that acetaminophen depletes the body’s natural reserves of glutathione, the “master” antioxidant responsible for mitigating free radical damage, which in turn protects the body against oxidative damage, inflammation and serious injury to the brain and other vital organs. Because it is incredibly toxic to the liver, Tylenol consumption prompts the body to use large amounts of glutathione to diminish this toxicity, which leaves the body more prone to developing the symptoms commonly attributed to autism.

“Many children with ASD (autism spectrum disorders) have poor transsulfuration and methylation — they can’t make glutathione and even worse, they can’t activate many neurotransmitters in the brain,” writes Dr. Erika Krumbeck, N.D., for Montana Whole Health. “[T]his is why Tylenol could possibly trigger autism in kids who are genetically susceptible.”